Our present invention relates to an apparatus for the trimming of strip, especially metal strip, and for cutting up the scrap which is produced by the strip trimming.
In the field of strip trimming it is known to provide a pair of trimmers on opposite sides of a strip processing line, especially a line for processing metal strip, to trim off edge portions of the strip. For that purpose, the trimmers may be provided with turntables which can have trimming heads on opposite sides thereof and which are rotated from trimming positions in which respective heads engage the strip, into readiness positions in which the cutters of the head can be replaced while another head is effective for trimming action.
Metal strip, metal sheets and metal plates are usually trimmed alongside edges to form a strip or sheet of a constant width and to remove strip or sheet irregularities or defects which tend to be represent along the edges of the strip or sheet to be trimmed. The trimming of metal strip, for example, is generally carried out in a strip treatment line and has a trimmer on each side of the strip. Each of the trimming heads, in turn, may be a pair of circular blades which can be adjusted in a direction transverse to the path of travel of the strip to vary the cutting gap and the closest blade to the center of the strip can be adjusted to define the width of the strip.
The cutting gaps of the circular blade pair and the relative positioning of the upper and lower blades can be selected to minimize the cutting burrs which may be formed and to increase the blade life. The scrap which is cut off, also in strip-like fashion, is generally cut up itself into narrow bands of widths of up to 15 mm by scrap cutters.
The scrap cutters can have blade drums formed with peripheral blades which can interdigitate with one another. The scrip strips which are formed by trimming can pass through passages of the trimming head between the blade drums of the scrap cutter and there can be chopped up into pieces whose length is a function of the blade spacing on the periphery of the blade drum. The chopped scrap can fall on a conveyor and can be transported out of the treatment line, e.g. to a furnace or scrap collector for remelting.
As noted, the upper and lower blades of the trimming head undergo wear and must be replaced from time to time. For this purpose, the trimmer turntable positions one of the trimmer heads in an operating position in which it participates in trimming of the strip while the other trimming head is in a readiness position in which it can undergo maintenance, sharpening, replacement or some other procedure.
The turntable can thus have one trimming head in a working position and the other trimming head in a blade-replacement position. The changeover from one head to the other can take only one to two minutes.
In general, the blade life of the scrap chopping head is as a rule longer than the blade life of the blades of the trimming heads. As a result of this greater life, the double trimmer of a turntable is usually combined with a single scrap chopper. This, however, can lead to significant problems. For example, there can be a backup of the scrap in the scrap channel which can result in standstill of the strip processing line. Edge defects can result in premature blade failure even where precautions are taken. As a consequence, the strip treatment lines may be equipped with tandem scrap choppers to minimize the duration of operation of the trimmer. Strip treatment lines with strip choppers arranged in tandem do indeed usually provide one of the strip choppers in an operating position while the other is in a maintenance or preparatory position. The tandem constructions known in the art, however, occupy considerable space and tandem arrangements usually cannot be applied to existing treatment lines and treatment lines cannot generally be equipped with tandem choppers in many instances.
It has been proposed to provide a turntable with two trimming heads with spaced-apart scrap choppers oriented at an angle of 90xc2x0 to one another as seen in a plan view onto the turntable. This arrangement also requires a large amount of space, especially since the trimming heads and the choppers must be provided with the respective drives. Furthermore, relatively large turntables are required to provide, in addition to the two maintenance and blade replacement positions, appropriate mounts for the trimming heads and the chopping heads.
It is, therefore, the principal object of the present invention to provide an apparatus for trimming strip, especially metal strip, whereby the scrap which is produced can be cut up in a reliable and efficient manner but wherein the apparatus as a whole will be relatively compact and efficient.
Another object of this invention is to provide an apparatus for the trimming of strip and for cutting up the strip scrap which is produced whereby drawbacks of the aforedescribed systems are obviated.
It is also an object of this invention to provide a trimmer arrangement with improved scrap cutters such that the scrap cutters occupy a minimum of space and can operate reliably, efficiently and conveniently.
These objects and others which will become apparent hereinafter are attained, in accordance with the invention by providing a pair of trimming strip cutters, each of which is associated with a respective trimming head on the same side of a median plane through the turntable and such that the trimming strip or scrap cutter heads are all set at an angle of 180xc2x0 from one another on opposite directions about the axis and as seen in a plan view of the turntable.
While the trimming heads are practically aligned with one another across the turntable and on opposite sides of this plane, the trimming strip cutter heads or scrap cutter heads are located along a diagonal, i.e. a diameter through the axis which is inclined to the common axis of the trimming head and thus spaced from the trimming head in opposite directions on either side of this plane. This has the consequence that relatively small turntables can be used. Furthermore, only a single readiness position, corresponding to the maintenance or blade replacement position, is required for the respective trimming head and scrap cutter. The displacement between the positions requires only a 180xc2x0 rotation of the turntable to swing a respective trimming head and its scrap cutter from the operating position into the maintenance and blade replacement position and vice versa.
According to another feature of the invention, each turntable has only a single drive string for the trimming heads and the scrap cutting heads, the drive string as seen in a view lying at an angle of 90xc2x0 to the plane and parallel to the common axis of the trimming heads and perpendicular to a common plane of the respective trimming head and the respective scrap cutter. The drive string is provided with a coupling which can engage the drives for one of the trimming heads and the respective scrap cutting head in one angular position of the turntable and can engage a transmission or drive unit for the other cutting head, the respective scrap cutter in the other angular position of the turntable. The drive string can include a clutch half, usually a jaw clutch half, which can engage in a complementary jaw half of the respective trimming head and scrap cutter drive or transmission. The coupling halves of the turntable with which the clutch half of the drive can engage, are also located on a diagonal across the turntable.
It has been found to be advantageous to provide the two trimming heads and their respective trimming strip cutting heads of the respective turntable in a common housing so that the overall assembly has a compact, easily maintained and inexpensive construction with a high degree of reliability and convenience for trimming strip and cutting up the trimming waste.
Because of the arrangement of the trimming heads and the scrap cutting heads in a single housing, the trimming waste passages can be relatively small. This reduces the danger of blockage of the trimming waste movement significantly. The longer the trimming waste passage, the greater is the risk that the trimming waste will interfere with operation of the strip handling line.
According to a further feature of the invention, the trimming heads or at least their lower blades and the trimming waste-cutting heads or their blade drums are driven by a common drive or motor. This is facilitated by the integration of the trimming heads and trimming waste cutting heads in a single housing.
Of course the trimming heads can basically operate also by entrainment along with the traveling strip and without having special drives.
In a preferred embodiment of the invention, the strip width setting of the turntable is determined by the spacing between the upper blades of the two trimmers plus twice the cutting gap between the upper blades and the lower blades of the trimming head.
To the extent that the strip-width setting depends upon the positions of the upper blades, the upper blades themselves can be made adjustable while the lower blades are not individually adjustable although the distance between the upper and lower blades can be varied. For this reason the adjustment of the respective cutting gap and the overlap of respective upper and lower blades for the trimming is preferably effected by means of adjustment of the upper blades.
According to still another feature of the invention the cutting gap of the scrap cutting head can also be adjustable to optimize the blade life of the cutting drum of the trimming strip cutting head.
Finally, it has been found that the mean distance between the trimming head and the associated trimming strip cutting head should be less than 2.5 times the blade diameter of the cutting head and should be as small as possible so that between the trimming head and the scrap cutting head a blockage of the cutting waste should not occur or should be able to be removed in a short period of time.